$\dfrac{9}{12} - \dfrac{3}{10} = {?}$
Solution: $ = {\dfrac{9 \times 5}{12 \times 5}} - {\dfrac{3 \times 6}{10 \times 6}} $ $ = {\dfrac{45}{60}} - {\dfrac{18}{60}} $ $ = \dfrac{{45} - {18}}{60} $ $ = \dfrac{27}{60}$